package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;

import lombok.val;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate redisTemplate) {
        this.stringRedisTemplate = redisTemplate;
    }

    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        // 设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(time));
        // 写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback
     ,Long time, TimeUnit unit){
        String key = keyPrefix + id;
        // 1.从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            // 3.存在，直接返回;
            return JSONUtil.toBean(json,type);
        }
        // 判断命中的是否是空值
        if(json != null){
            // 返回错误信息
            return null;
        }
        // 4.不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        // 5.不存在，返回错误
        if(r == null){
            // 将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            // 返回错误
            return null;
        }
        // 6.存在，写入redis
        this.set(key,r,time,unit);

        // 7.返回
        return r;
    }


    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Class<R> type,Function<ID,R> dbFallback
    ,Long time, TimeUnit unit){
        String key = keyPrefix + id;
        // 1.从redis查询商铺缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            // 3.不存在，返回空值
            return null;
        }
        // 4.存在，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5.判断是否过期
        if(expireTime.isAfter(LocalDateTime.now())){
            // 5.1未过期，返回店铺信息
            return r;
        }
        // 5.2已过期，需要缓存重建
        // 6.缓存重建
        // 6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        // 6.2是否获取锁成功
        if (tryLock(lockKey)) {
            if (expireTime.isBefore(LocalDateTime.now())) {
                // 6.3成功，判断缓存是否过期，若过期，开启独立线程，实现缓存重建
                CACHE_REBUILD_EXECUTOR.submit(() ->{
                    try {
                        // 查数据库
                        R r1 = dbFallback.apply(id);
                        // 写入Redis
                        this.setWithLogicalExpire(key,r1,time,unit);
                    } catch (Exception e) {
                        throw new RuntimeException(e);
                    }
                    finally {
                        // 释放锁
                        unLock(lockKey);
                    }
                });
            }
        }
        // 6.4返回商铺信息
        return r;
    }

    // 获取锁
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    // 释放锁
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

}
